1. Field of the Invention
This invention relates to a transmission and a rolling bearing with seal plate for that transmission, and more particularly to improvements in the transmission (including a transaxle) for an automobile, truck, or a special kind of vehicle such as a tractor or fork lift, and to improvements in the rolling bearing with seat plate that is installed in that kind of transmission. The transmission which is the object of this invention, includes a manual transmission, as well as all kinds of automatic transmission such as planetary-gear type, belt type and toroidal type.
2. Description of the Related Art
An example of an automatic transmission that has a rolling bearing with seal plate installed in it as disclosed in U.S. Pat. No. 4,309,916, is shown in FIG. 3. In the manual transmission, simply shown in FIG. 3, lubrication oil (transmission oil) 25 is stored in a casing 24, and an input shaft 26 and output shaft 27 are arranged in the casing 24 such that they are concentric with each other and can freely rotate relative to each other. Moreover, there is also a transmission shaft 28 located inside the casing 24 such that it is parallel with respect to the input shaft 26 and output shaft 27. The input shaft 26, output shaft 27 and transmission shaft 28 are supported respectively by a rolling bearing 1 with seal plate such that they can rotate freely.
A drive gear 29, which is a power transmission member on the drive side, is supported on the input shaft 26. Also, on the output shaft 27, there are follower gears 30a to 30d, which are power transmission members on the follower side, and they are each supported by a synchro mesh mechanism (not shown in the figure). During operation, only one of the aforementioned follower gears 30a to 30d rotates together with the output shaft 27, and the other follower gears rotate relative to the output shaft 27.
Moreover, at respective sections of the transmission shaft 28 which face the drive gear 29 and follower gears 30a to 30d, there are transmission gears 31a to 31e which are supported such that they rotate freely with the transmission shaft 28. These transmission gears 31a to 31c are made to mesh with the drive gear 29 and follower gears 30a to 30d directly or by way of an idler gear 32 for moving back.
As described above, a plurality of rotating shafts and many gears are assembled in the automobile transmission. These rotating shafts and gears are supported by rolling bearings, such as ball bearings or cylindrical roller bearings, such that they rotate freely with respect to the housing and support shaft. On the inside of this kind of transmission, there is a lot of foreign matter, such as grinding scraps or grinding agent, that is caused in processing the gears or housing etc., and adheres to and remains on the gears or housing, or as abrasive material that is generated in the section where the gears mesh during operation. When this kind of foreign matter gets inside the rolling bearing, indentations are formed by the foreign matter on the rolling contact surfaces, and these indentations make it easier for the surfaces to become damaged due to fatigue. Therefore, conventionally, a rolling bearing 1 with seal plate, as shown in FIG. 4, is used as the rolling bearing for use in conditions where there exist much metallic foreign matter as described above.
This rolling bearing 1 with seal plate comprises: an inner race 3 having inner ring raceway 2 of the deep-groove type formed around its outer peripheral surface in the center in the axial direction (left and right direction in FIG. 4), an outer race 5 arranged concentric with the inner race 3 and having an outer ring raceway 4 of the deep-groove type formed around its inner peripheral surface in the middle in the axial direction, and a plurality of rolling bodies or balls 6 located between the inner ring raceway 2 and outer ring raceway 4 such that they can rotate freely. These balls 6 are supported inside a plurality of pockets 8 which are formed in a retainer 7, such that each ball 6 can rotate freely itself in each pocket 8. Instead of the balls 6, shown in the example in the figure, it is also possible to use cylindrical or tapered rollers as the rolling bodies.
Moreover, attachment grooves 9 are formed around the inner peripheral surface on both ends of the outer race 5, and the outer peripheral edges of the seal plates 10 are attached to the attachment grooves 9. These seal plates 10 are generally circular shaped and comprise a circular-shaped metal core 11 that is made of a metal plate such as a steel plate and an elastic member 12 such as a rubber-like elastomer which is reinforced by the metal core 11. The outer peripheral edge of the elastic member 12 is made to protrude outward in the radial direction (up and down direction in FIG. 4) only a little from the outer peripheral edge of the metal core 11, and this protruding section fitted into and attached to the attachment groove 9.
On the other hand, the inner peripheral edge of the elastic member 12 is made to protrude sufficiently inward in the radial direction from the inner peripheral edge of the metal core 11 to form a seal lip 13 in the protruding section. In addition, seal grooves 14 are formed on the outer peripheral surface on both ends of the inner race 3 such that they are defined by an inner wall surface 15 and outer wall surface 16, and the tip edge of this seal lip 13 comes in contact with the inner-wall surface 15 of seal grooves 14. Here, the tip edge of this seal lip 13 is forked with reference to the axial direction, such that even when the inner race 3 or outer race 5 is displaced in the axial direction, the tip edge of this seal lip 13 is always in sliding contact with at least one of the inner wall surface 15 and outer wall surface 16 of the seal groove 14.
With the rolling bearing 1 with seal plate, constructed as described above, relative rotation of the member around which the inner race 3 is attached and the member inside which the outer race 5 is attached is allowed by the rolling of the balls 6. Moreover, the pair of seal plates 10, whose outer peripheral edges are fitted into the inner peripheral surface on both ends of the outer race 5, prevents the grease that is filled inside the space 17 where the balls 6 are located, from leaking out, and also prevents foreign matter on the outside such as dirt, oil, or water from getting into the space 17 where the balls 6 are located.
In the case of the seal plate 10 comprising the metal core 11 and the elastic member 12 made of a rubber-like elastomer or the like, not only is the cost high, but it is also difficult to make the seal plate 10 more lightweight and reusable (recyclable). In other words, weight of the seal plate 10 is increased by the amount of the metal core 11 that is used to reinforce the elastic member 12. In addition, since the elastic member 12 is attached to the metal core 11, the manufacturing cost increases, and the seal plate 10 becomes more difficult to reuse.
In the case of just reducing the manufacturing cost, it is considered to be possible to use inexpensive nitrile rubber (NBR) as the elastic member 12. However, when NBR is used in the high-temperature conditions in an automobile transmission or in an environment with constant contact with oil, the material soon becomes hard and in poor condition, and thus there is a possibility that a proper seal cannot be maintained over a long period of time.
On the other hand, in the case of using an acrylic rubber or fluorine-contained rubber which comparatively does not easily become hard or degrade in high-temperature environment, the cost and weight increase and reusability becomes difficult, so from the aspect of protecting the environment, it is not preferred.
On the other hand, when the seal plate is made of synthetic resin, it becomes easier to reduce the weight of the seal plate and improve its reusability, and it also becomes possible to lower the manufacturing cost since mass production can be improved by use of a die.
However, when the seal plate is constructed in this way using synthetic resin, it becomes difficult to secure the seal performance of this seal plate. In other words, since it is more difficult for synthetic resin to elastically deform than rubber, even when the seal plate is made of the synthetic resin in the shape shown in FIG. 4, such that the tip edge of the seal lip on the inner peripheral edge of the seal plate 10 is constantly in sliding contact with either the inner wall surface 15 or outer wall surface 16 of the seal groove 14, it is difficult to attach the seal plate to the outer race 5 while the seal lip is extended on the inside of the seal groove 14.
Moreover, when an elastic force is applied to the tip edge of the seal lip, in other words, when the tip edge of the seal lip comes in sliding contact with the inner wall surface 15 of the seal groove 14 having interference in the axial direction, it is easy for the resistance (load torque) of the rolling bearing with seal plate to become large by the amount that it is more difficult for the synthetic resin to deform elastically in comparison to rubber.
An object of this invention, taking the aforementioned problems into consideration, is to provide a rolling bearing with seal plate for a transmission in which the seal plate is made of synthetic resin, and it is always possible for the peripheral edge of the seal plate to slide freely over the entire surface of an inner race or outer race as required even when the race is displaced in the axial direction.